Add missing aliases for \p{Present_In}

\p{Present_In} is a Perl extension of the Unicode Age property, added
because knowing the exact Unicode version in which a code point became
assigned is rarely what you want; much more frequently you want to know
if the code point exists in the version or not.  (Since this extension
was added, Unicode changed their language to declare that the Age
property should be interpreted in pattern matching, not as described,
but as Perl's Present_In is.  But  I chose to not change Age, to avoid
backwards compatibility issues, and this way, a coder can choose which
thing s/he wanted.)

Unicode typically has synonyms (aliases) for each value a property can
tak on, so \p{Age=6.1} and \p{Age=V61_1} mean the same thing.

Prior to this commit, neither \p{Present_In=1_1} nor \p{Present_In=NA}
worked.